1. Field of the Invention
The present invention relates generally to artificial firelogs and particularly to an artificial firelog effecting cost savings by allowing the amount of relatively expensive petroleum and/or non-petroleum wax components in a firelog to be reduced without an appreciable decrease in heating value or flame intensity.
2. Description of the Related Art
Fireplaces have been used in homes over the years for providing heat as well as to provide a desired ambience. While wood and coal have been the primary fuels for burning in fireplaces, there is an increasing demand for manufactured or artificial fireplace logs (firelogs). These firelogs are easier to purchase and store, provide better heating values (BTU/lb) than wood or coal, are easier to light, safer to use with virtually no maintenance during burning, and can be used to build fires of a known duration, generally from 2 hours to more than 4 hours.
Artificial firelogs are typically manufactured by combining a carrier material, usually particles of cellulosic origin, with a combustible binder/fuel. The cellulosic material may be sawdust, or a mixture of sawdust with other combustible materials of varying proportion. The binder/fuel typically consists of a suitable blend of waxes, either alone or in combination with other combustible materials. Additives imparting desired combustion characteristics, appearance, and other attributes may be combined with the basic ingredients. Such additives may include chemicals designed to color or otherwise modify or retard the flame, add aroma or crackling sounds, or otherwise change the burning characteristics to more closely mimic the burning of natural logs. Following thorough mixing of the ingredients, the resulting mixture is formed into suitable, log-like shapes by extrusion, molding or compression, in either a batch or continuous process.
U.S. Pat. Nos. 3,297,419; 6,017,373; 6,136,054; 5,868,804; 4,333,738; 4,326,854; 3,843,336; and 4,040,796, incorporated herein by reference in their entireties, provide examples of known artificial firelog compositions, configurations and methods of manufacture.
Artificial firelogs are often manufactured from blends of approximately about 50% to about 60% (by weight) of petroleum waxes and about 40 to about 50% (by weight) of cellulosic fibers. The petroleum wax constituent, which may comprise paraffin wax or slack wax by way of example, provides the principal fuel content for the firelog and contains about twice the BTU energy value per unit mass as the cellulosic fibers. The high wax content allows easy ignition of the firelog, long burn time, and aesthetically pleasing flame height and intensity. The main disadvantages of firelogs with high wax content is added cost, an increased burn rate providing an unsatisfactory overall burn time, and/or high flames which can be a safety hazard.
In recent years, there has been dramatic inflation in the cost of petroleum products, including refined products such as petroleum waxes. Between January 2004 and July 2006, for example, petroleum wax costs increased 120%, making it less economic for firelog manufacturers to use petroleum wax in their products. Thus there is a real need to identify viable, practical, and cost-effective alternatives to petroleum waxes which can be used, either in full or in part, in firelog manufacture.
Coffee ground has energy content in excess of about 10000 BTU/lb, which is about 25% higher energy potential (BTU) than a typical wood fiber. U.S. Pat. No. 6,113,662 disclosed that a firelog could be produced with reduced wax content by using spent dried coffee grounds as a fuel source and that, if coffee grounds were used as the principal constituent of the fuel, less combustible binder was required to achieve the equivalent calorific value of a typical sawdust firelog having high wax content. In addition to coffee grounds having a higher calorific value, the grounds apparently also had a higher volatile/fixed carbon ratio than that of wood-based particulates and, for that reason provided superior flame performance. It was concluded from these results that, since dried spent coffee grounds contribute greater calorific value and volatile/fixed carbon ratio than wood sawdust, the coffee firelog required much less wax binder than traditional formulations used for wood sawdust-wax firelogs.
While the burn characteristics of coffee grounds disclosed in U.S. Pat. No. 6,113,662 can make them an appealing material to substitute for wood fibers in firelogs, the higher calorific value and volatile/fixed carbon ratio of the coffee grounds that allowed the wax reduction was probably not the only or most important property that contributes to wax reduction. Coffee grounds also absorb approximately five times less oil or wax than highly absorbent “spongy-like” softwood fibers, and there are many other oil retaining fiber and mineral materials having non-absorbent, increased calorific value and elevated volatile/fixed carbon ratio properties similar to those of coffee grounds.
Similar phenomena related to absorption/adsorption characteristics of cellulosic fibers, for example were noted in U.S. Pat. No. 4,326,854, which disclosed replacing part or all of the sawdust in a firelog with a cellulosic material that absorbed moisture less readily, or was less affected by absorbed water, in order to reduce the swelling and cracking on firelogs. When cellulosic materials such as peanut shell fines, cocoa bean shell fines, coconut shell or walnut shell fines, bagasse or paper pulp were used as a replacement for the wood sawdust in a firelog, either in part or in whole, a firelog less subject to swelling and cracking was typically observed. However, the fuel used in the firelogs was a combustible liquid by-product that had to be chemically solidified, by either polymerization or neutralization by the addition of various chemicals prior to use, processes that would typically increase the cost and complexity of manufacturing a product such as a firelog.
Thus, an object of the present invention is to provide more cost effective raw materials for use in the manufacture of firelogs, materials that allow for the reduction in costly petroleum wax by substituting other, more cost effective materials that make up for the BTU energy content lost from a reduction or elimination of the higher BTU petroleum wax.